As a child, Masahiro Setagawa hated the idea of heroes, as no one had ever attempted to save him from his own miserable existence. As a teenager, he became an errand boy for delinquents and had no desire to change his ways before meeting the "Bear Killer," Kousuke Ooshiba, a man with no qualms about beating up evildoers. After discovering his identity, Setagawa became Kousuke's underling and also struck up a friendship with his brother Kensuke.

A few years later, the relationship between Kousuke and Setagawa has not evolved beyond their initial master and subordinate arrangement. But after Setagawa sees Kensuke with his boyfriend Asaya Hasekura, and a misunderstanding arises on the part of Kousuke, Setagawa realizes that his feelings for his mentor may not be as clear cut as previously thought.